update transaction-payment (#1021)

modules/transaction-payment/src/lib.rs

@@ -644,6 +644,11 @@ where
 		let tip = self.0;
 		let fee = Pallet::<T>::compute_fee(len as u32, info, tip);
 
+		// Only mess with balances if fee is not zero.
+		if fee.is_zero() {
+			return Ok((fee, None));
+		}
+
 		let reason = if tip.is_zero() {
 			WithdrawReasons::TRANSACTION_PAYMENT
 		} else {
@@ -758,12 +763,10 @@ where
 				// is gone in that case.
 				Err(_) => payed,
 			};
-			let imbalances = actual_payment.split(tip);
+			let (tip, fee) = actual_payment.split(tip);
 
 			// distribute fee
-			<T as Config>::OnTransactionPayment::on_unbalanceds(
-				Some(imbalances.0).into_iter().chain(Some(imbalances.1)),
-			);
+			<T as Config>::OnTransactionPayment::on_unbalanceds(Some(fee).into_iter().chain(Some(tip)));
 		}
 		Ok(())
 	}